With a calorie-restriction diet, you reduce the number of calories you typically consume in a day. This type of diet should allow you to cut calories without depriving your body of essential nutrients, the U.S. National Institute on Aging says.

With a fasting diet, on the other hand, you limit food or stop eating altogether during periods of the day. Since there's less time for eating, you're actually limiting calories at the same time, the agency notes.

In research studies, rodents and other animals were given 10 percent to 40 percent fewer calories than usual but provided with all necessary nutrients. Many lived longer and had lower rates of several diseases, notably cancer, the agency says.

Not every study showed these same benefits, the institute says, noting that more research is needed.